Asking Google that question sees this answer at hit number two on the first page.
Every Wi-Fi network transmits and receives data on a certain frequency, or channel. As Wi-Fi data is digital, many different devices can communicate successfully on the same channel.
The full, detailed, response being found here: https://support.zen.co.uk/kb/Knowledgebase/Broadband-Understanding-Wireless-Channels
Hope that helps.